Ultrasonic vibration method and ultrasonic vibration apparatus

ABSTRACT

An ultrasonic vibration method and an ultrasonic vibration apparatus, which do not have a directional property in the direction of vibrations, are disclosed. A pair of ultrasonic horns ( 11 ), ( 12 ), each having an ultrasonic vibrator ( 13 ), ( 14 ) provided at an end portion thereof, are disposed in an intersecting relationship to each other, and the composite vibrations of transverse vibrations produced by the pair of ultrasonic horns ( 11 ), ( 12 ) when the other ultrasonic horns ( 12 ), ( 11 ) are excited to generate longitudinal vibrations are extracted at the intersecting point of the pair of horns ( 11 ), ( 12 ) and applied to a contact object member through a presser ( 22 ).

TECHNICAL FIELD

This invention relates to an ultrasonic vibration method and anultrasonic vibration apparatus and, more particularly, to an ultrasonicvibration method and an ultrasonic vibration apparatus wherein a pair ofultrasonic horns coupled in an intersecting relationship to each otherare used.

BACKGROUND ART

A bonding apparatus and a bonding method for an electronic part withbumps which utilizes ultrasonic vibrations are disclosed, for example,in Japanese Patent Laid-Open No. Hei 11-45912. Here, a pair of horns aredisposed in an opposing relationship to each other on a common axis, anda piezoelectric element is attached to each of the horns. Further, anattracting tool is provided at the center of a narrow connecting portionintermediate between the opposing horns, and a semiconductor chip havingbumps thereon is held by the attracting tool. Besides, the semiconductorchip here is resiliently held by and between a spring and a rib from adirection substantially perpendicular to the direction of the axis ofthe horns.

In the bonding apparatus and the bonding method described above, thesemiconductor chip is subject to vibrations in the axial direction ofthe horns by the horns. In an initial stage, when the semiconductor chipis moved in the vibration direction with respect to a board, oxide filmsof the bumps and electrodes are broken. Then, as the bonding proceeds,the semiconductor chip slips with respect to the holding means formedfrom the spring and the rib as a result of an increase of the bondingforce between the bumps and the electrodes, thereby to connect the bumpsof the semiconductor chip and the electrodes of the board to each other.

Such an ultrasonic bonding apparatus as disclosed in Japanese PatentLaid-Open No. Hei 11-45912 has a problem in that, where it is used forbonding of a semiconductor chip, it sometimes fails to bond asemiconductor device of the type wherein a plurality of bumps arearranged in an arbitrary arrangement in such conditions that the bondingforce of all of the bumps is higher than a desired value and nosignificant mechanical defect occurs. The ultrasonic bonding apparatushas a problem that, for example, if ultrasonic vibrations are applied toa semiconductor chip wherein bumps are arranged along a periphery of anelectrode face of a semiconductor bare chip such that the vibrationdirection thereof is the same direction as that of one side of therectangular bare chip, then if the bonding conditions are optimized sothat the bonding strength of all bumps may be higher than apredetermined value, then those bumps disposed along the sides extendingin the direction perpendicular to the application direction of theultrasonic vibrations, particularly those bumps which are at cornerportions of the rectangle of the bare chip, are likely to suffer fromcratering.

Further, the ultrasonic bonding apparatus has a problem that, if thebonding conditions are set conversely so that such cratering asmentioned above may not occur with any of the bumps, then the bondingstrength of those bumps that are disposed on the sides of thesemiconductor chip which extend in parallel to the application directionof the ultrasonic vibrations does not reach a sufficient value. Such aphenomenon as just described appears conspicuously, particularly where aboard having a low hardness such as, a glass epoxy type board is used asa mounting substrate.

The present invention has been made in view of the problems describedabove, and it is an object of the present invention to provide anultrasonic vibration method and an ultrasonic vibration apparatus bywhich, where the apparatus is used as a bonding apparatus for asemiconductor chip wherein a plurality of bumps are arranged in anarbitrary arrangement, the bumps can be bonded while a sufficientbonding strength is assured without causing mechanical damage such ascratering to occur with all the pad electrodes to be electricallyconnected.

DISCLOSURE OF INVENTION

The present invention relates to an ultrasonic vibration methodcharacterized in that a pair of ultrasonic horns are coupled in anintersecting relationship to each other, and a first one of theultrasonic horns is excited to longitudinally vibrate in a lengthwisedirection thereof to cause a second one of the ultrasonic horns togenerate transverse vibrations while the second ultrasonic horn isexcited to longitudinally vibrate in a lengthwise direction thereof tocause the first ultrasonic horn to generate transverse vibrations, suchthat composite vibrations of the transverse vibrations of the pair ofultrasonic horns that are produced at the intersecting coupling positionof the pair of ultrasonic horns are used as an output.

Here, the pair of ultrasonic horns may intersect substantiallyperpendicularly with each other and produce the composite vibrationswithin a plane substantially in parallel to the plane which includes thepair of ultrasonic horns. A presser may be provided at the intersectingcoupling position of the pair of ultrasonic horns and projectedsubstantially perpendicularly to the plane, which includes the pair ofultrasonic horns; and, the presser may be pressed against a contactobject member to transmit the composite vibrations to the contact objectmember. The contact object member may be bonded to another member by thecomposite vibrations.

A pair of ultrasonic vibrators for individually providing vibrations tothe pair of ultrasonic horns may be provided, and the phase relationshipbetween ultrasonic signals to be applied to the pair of ultrasonicvibrators may be adjusted. Adjustment of the phase of one of the pair ofultrasonic vibrators may be performed to adjust the phase relationshipbetween the signals to the pair of ultrasonic vibrators. The amplitudesor the angular velocities of or the phase difference between theultrasonic signals to be applied to the pair of ultrasonic vibrators maybe adjusted to vary the locus of the composite vibrations in a planeparallel to the plane, which includes the pair of ultrasonic horns. Thepair of ultrasonic horns may have a length substantially equal to thewavelength of ultrasonic waves which propagate in the pair of ultrasonichorns or substantially equal to an integral number of times thewavelength. Each of the pair of ultrasonic horns may be fixed at leastat a position of a node. The pair of ultrasonic horns may intersect withand be coupled to each other, each at a substantially middle portion inthe lengthwise direction thereof, such that the amplitude of thelongitudinal vibrations is maximum at the intersecting couplingposition, and each may be fixed by fixing means at a position spaced bya half wavelength or a distance of the sum of a half wavelength and anintegral number of times one wavelength from the intersecting couplingposition

The present invention according to a first principal aspect relating toan ultrasonic vibration apparatus relates to an ultrasonic vibrationapparatus characterized in that it comprises a pair of ultrasonic hornscoupled in an intersecting relationship to each other, and a first oneof the ultrasonic horns is excited to longitudinally vibrate in alengthwise direction thereof to cause a second one of the ultrasonichorns to generate transverse vibrations while the second ultrasonic hornis excited to longitudinally vibrate in a lengthwise direction thereofto cause the first ultrasonic horn to generate transverse vibrations,such that composite vibrations of the transverse vibrations of the pairof ultrasonic horns that are produced at the intersecting couplingposition of the pair of ultrasonic horns are used as an output.

Here, the pair of ultrasonic horns may intersect substantiallyperpendicularly with each other and produce the composite vibrationswithin a plane substantially in parallel to the plane which includes thepair of ultrasonic horns. The ultrasonic vibration apparatus may furthercomprise a presser provided at the intersecting coupling position of thepair of ultrasonic horns and projected substantially perpendicularly tothe plane, which includes the pair of ultrasonic horns; and, the pressermay be pressed against a contact object member to transmit the compositevibrations to the contact object member. The contact object member maybe bonded to another member by the composite vibrations.

The ultrasonic vibration apparatus may further comprise a pair ofultrasonic vibrators for individually providing vibrations to the pairof ultrasonic horns, and the phase relationship between ultrasonicsignals to be applied to the pair of ultrasonic vibrators may beadjusted. Adjustment of the phase of at least one of the pair ofultrasonic vibrators may be performed. The amplitudes or the angularvelocities of or the phase difference between the ultrasonic signals tobe applied to the pair of ultrasonic vibrators may be adjusted to varythe locus of the composite vibrations in a substantially same plane.

The pair of ultrasonic horns may have a length substantially equal tothe wavelength of ultrasonic waves which propagate in the pair ofultrasonic horns or substantially equal to an integral number of timesthe wavelength. Each of the pair of ultrasonic horns may be fixed atleast at a position of a node by fixing means. The pair of ultrasonichorns may intersect with and be coupled to each other, each at asubstantially middle portion in the lengthwise direction thereof suchthat the longitudinal vibrations exhibit a maximum amplitude at theintersecting coupling position, and each may be fixed by fixing means ata position spaced substantially by a half wavelength or a distance ofthe sum of a half wavelength and an integral number of times onewavelength from the intersecting coupling position. An odd-numberedorder natural frequency of the transverse vibrations of the firstultrasonic horn may substantially coincide with the frequency of anultrasonic vibrator of the second ultrasonic horn, which intersects withthe first ultrasonic horn, such that the transverse vibrations thereofsubstantially resonate with the ultrasonic vibrations of the secondultrasonic horn.

The present invention according to another principal aspect relating toan ultrasonic vibration apparatus relates to an ultrasonic vibrationapparatus characterized in that it comprises a pair of ultrasonic hornscoupled in a substantially intersecting relationship to each other in apredetermined plane, an ultrasonic vibrator attached to an end portionof each of the ultrasonic horns, an ultrasonic oscillator for supplyingultrasonic signals to the pair of ultrasonic vibrators, and a presserprovided at the intersecting coupling position of the pair of ultrasonichorns for being pressed against a contact object member, and that thepair of ultrasonic horns are excited to individually vibratelongitudinally such that the contact object member is bonded through thepresser by composite vibrations of transverse vibrations produced at theintersecting coupling position.

Here, the ultrasonic vibration apparatus may further comprise phaseadjustment means for adjusting the phase of the ultrasonic signals to beapplied to the pair of ultrasonic vibrators. The phase adjustment meansmay be provided between at least one of the ultrasonic vibrators and theultrasonic oscillator. The amplitudes or the angular velocities of orthe phase difference between the ultrasonic signals to be applied to thepair of ultrasonic vibrators may be adjusted to vary the locus of thecomposite vibrations in the predetermined plane.

One of the ultrasonic horns may have a length substantially equal to thewavelength of ultrasonic waves which propagate in the ultrasonic hornsor substantially equal to an integral number of times the wavelength.Each of the pair of ultrasonic horns may be fixed at least at a positionof a node by fixing means. The pair of ultrasonic horns intersect withand may be coupled to each other each at a substantially middle portionin the lengthwise direction thereof such that the amplitude of thelongitudinal vibrations is maximum at the intersecting couplingposition, and each may be fixed by fixing means at a position spaced bya half wavelength or a distance of the sum of a half wavelength and anintegral number of times one wavelength from the intersecting couplingposition. An odd-numbered order natural frequency of the transversevibrations of a first one of the ultrasonic horns may substantiallycoincide with the frequency of the ultrasonic vibrator of a second oneof the ultrasonic horns which intersects with the first ultrasonic horn,such that the transverse vibrations thereof substantially resonate withthe ultrasonic vibrations of the second ultrasonic horn.

A preferred form of the invention included in the present inventionrelates to an ultrasonic vibration method and an ultrasonic vibrationapparatus for bonding a semiconductor chip which forms a flip chip IC toan electronic circuit board using ultrasonic waves, configured such thatit comprises a pair of ultrasonic oscillators, a phase adjustmentapparatus for adjusting the phase difference between ultrasonic signalsoutputted from the ultrasonic oscillators, two ultrasonic vibrators forgenerating ultrasonic waves in response to the ultrasonic signals fromthe ultrasonic oscillator, and a pair of ultrasonic horns intersectingin a substantially cross-shape with each other on an X-Y plane; andultrasonic vibrations are attached individually to the ultrasonic hornsand the amplitude and the angular velocity of the vibrations in theX-axis direction, the amplitude and the angular velocity of thevibrations in the Y-axis direction and the phase difference between thevibrations in the X-axis direction and the Y-axis direction areindividually adjusted to appropriate values such that the semiconductorchip is pressed in vibrations against the electronic circuit board withan optimum locus in the X-Y plane to improve the bonding strength andthe uniformity in bonding between the semiconductor chip and theelectronic circuit board.

Here, the ultrasonic horns for the X-axis direction and the Y-axisdirection that are coupled in an intersecting relationship in asubstantially cross-shape to each other may have a length substantiallyequal to an integral number of times the wavelength of ultrasonic waveswhich propagate in the ultrasonic horns; and, besides each may be fixedat a position spaced by a ½ wavelength or a distance of the sum of a ½wavelength and a distance of an integral number of times one wavelengthfrom the center of the ultrasonic horns. Further, the pair of ultrasonichorns disposed in an intersecting relationship with each other generatesuch vibrations that longitudinal vibrations in one of the X-axisdirection and the Y-axis direction by ultrasonic waves cause theultrasonic horn for the other of the X-axis direction and the Y-axisdirection to generate transverse vibrations, and composite vibrationsproduced by synthesis of the transverse vibrations of the ultrasonichorn for the X-axis direction and the transverse vibrations of theultrasonic horn for the Y-axis direction form an arbitrary locus in theX-Y plane. Further, where an odd-numbered order natural frequency of thetransverse frequency of the ultrasonic horn in this instance is setcoincident with the frequency of the ultrasonic oscillator, thetransverse vibrations resonate with the ultrasonic vibrations.Consequently, an ultrasonic vibration apparatus, which generatespreferred vibrations is obtained.

Where such an ultrasonic vibration method and an ultrasonic vibrationapparatus as described above are used for bonding of a semiconductorchip formed from a flip chip IC and an electronic circuit board, even ifthe arrangement of bumps of the semiconductor chip differs in variousmanners, since the direction of the ultrasonic vibrations includescomponents of the two directions of the X-axis direction and the Y-axisdirection, a bonding quality having a stable bonding strength and auniformity in bonding is achieved without being influenced by thedirection of arrangement of the bumps.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of an essential part of an ultrasonicvibration apparatus to which an ultrasonic vibration method of anembodiment is applied;

FIG. 2 is a front elevational view of an essential part of theultrasonic vibration apparatus;

FIG. 3 is a sectional view taken along line A—A of FIG. 2;

FIG. 4 is a plan view similar to FIG. 3 but illustrating transversevibrations generated by a pair of horns extending perpendicularly toeach other;

FIGS. 5(A) to 5(I) are plan views showing a locus of the vibrations;

FIG. 6 is a front elevational view showing a semiconductor chip in abonded state;

FIG. 7 is a bottom plan view of the semiconductor chip held by apresser;

FIG. 8 is a vertical sectional view of the bonded semiconductor device;

FIG. 9 is a plan view of an essential part of an ultrasonic vibrationapparatus of another embodiment; and

FIG. 10 is a plan view of an essential part of an ultrasonic vibrationapparatus of a further embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

FIGS. 1 to 3 show a general configuration of an ultrasonic vibrationapparatus to which an ultrasonic vibration method according to anembodiment of the present invention is applied. The present ultrasonicvibration apparatus includes a pair of ultrasonic horns 11 and 12disposed perpendicularly to each other, as shown in FIG. 1. Here, theultrasonic horn 11 is disposed in the direction of an X-axis while theultrasonic horn 12 is disposed in the direction of a Y-axis. Ultrasonicvibrators 13 and 14 are attached to end portions of the pair ofultrasonic horns 11 and 12, respectively. The ultrasonic vibrators 13and 14 cause the ultrasonic horns 11 and 12 to generate vibrations inthe lengthwise directions, that is, in the longitudinal directions,respectively.

The ultrasonic horn 11 is connected at an intermediate position betweenthe center and each of the opposite ends thereof, that is, at each nodalpoint, to fixed rods 16 through arms 15 on the opposite sides thereof.Similarly, the ultrasonic horn 12 for the Y-axis direction is coupled atan intermediate position between a middle portion and each of theopposite ends in the longitudinal direction thereof to fixed rods 18through arms 17 on the opposite side thereof. The fixed rods 16 and 18are securely mounted on a lower face of a support plate 19 shown in FIG.2. The support plate 19 is securely mounted at an end portion of avertical shaft 20 which is movable upwardly and downwardly in thedirection of a Z-axis A presser 22 is mounted on a lower face at anintersecting position of the pair of ultrasonic horns 11 and 12.

In order to cause the ultrasonic horns 11 and 12 to vibratelongitudinally, a control circuit 25 shown in FIG. 3 is provided. Thecontrol circuit 25 is connected to a pair of ultrasonic oscillators 27and 28. Here, a phase adjuster 29 is connected between the ultrasonicoscillator 28 for the Y-axis direction and the control circuit 25, sothat a predetermined phase difference may be produced between outputs ofthe pair of ultrasonic oscillators 27 and 28.

In such a configuration as described above, the ultrasonic oscillators27 and 28 supply ultrasonic signals to the ultrasonic vibrators 13 and14, respectively, under the control of the control circuit 25. The phasedifference between the pair of ultrasonic oscillators 27 and 28 in thisinstance is adjusted arbitrarily by means of the phase adjuster 29.

The ultrasonic horn 11 for the X-axis direction generates longitudinalvibrations in the longitudinal direction thereof, as seen in FIG. 3, inresponse to the ultrasonic signal applied to the ultrasonic oscillator13. The longitudinal vibrations exhibit maximum amplitude at theopposite ends and the central portion of the ultrasonic horn 11 andexhibit an amplitude of 0 at each of the positions at which theultrasonic horn 11 is fixed by a pair of fixed rods 16. From suchlongitudinal vibrations, as just described, the ultrasonic horn 12 forthe Y-axis direction, which extends perpendicularly to the ultrasonichorn 11 for the X-axis direction, produces transverse vibrations.

Similarly, the ultrasonic oscillator 14 excites the ultrasonic horn 12for the Y-axis direction to generate longitudinal vibrations in responseto the ultrasonic signal applied from the ultrasonic oscillator 28.Consequently, the ultrasonic horn 11 for the X-axis direction generatestransverse vibrations. FIG. 4 illustrates the transverse vibrations ofthe pair of ultrasonic horns 11 and 12. Composite vibrations of thetransverse vibrations are extracted from the intersecting couplingposition of the pair of ultrasonic horns 11 and 12. In particular, thecomposite vibrations are extracted at the central position of theultrasonic horns 11 and 12 at which the presser 22 is provided. Suchcomposite vibrations are composite vibrations with which an end portionof the composite vibrations shown in FIG. 4 draws an arbitrary locusdepending upon the amplitudes and angular velocities of and the phasedifference between the ultrasonic vibrations applied to the ultrasonichorn 11 for the X-axis direction and the ultrasonic horn 12 for theY-axis direction.

In this manner, with the ultrasonic vibration method and the ultrasonicvibration apparatus of the present embodiment, ultrasonic signalsoutputted from the pair of ultrasonic oscillators 27 and 28 are appliedto the ultrasonic vibrators 13 and 14, respectively. At this time, thephases of the two ultrasonic signals are adjusted by means of the phaseadjuster 29. It is to be noted that the phase adjuster may be formedfrom a timer which displaces the starting time of oscillation.

The pair of ultrasonic horns 11 and 12, to which the ultrasonicvibrators 13 and 14 are attached, respectively, are disposed such thatthe directions of vibrations thereof may be perpendicular to each other.Now, it is assumed that the vibrations applied to the ultrasonic horn 11for the X-axis direction are x=Acosω₁t in the X-axis direction.Meanwhile, it is assumed that the vibrations in the Y-axis directionapplied by the ultrasonic oscillator 14 are y=Bcos(ω₂t−α). It is to benoted here that t represents time.

The amplitudes A and B of the two ultrasonic horns 11 and 12 can be setfreely by adjusting the intensity of the ultrasonic signals of the pairof ultrasonic oscillators 27 and 28. Also the phase difference α betweenthe vibrations in the two directions can be adjusted arbitrarily bymeans of the phase adjuster 29 described hereinabove.

The angular velocity ω₁ of the vibrations in the X-axis direction andthe angular velocity ω₂ of the vibrations in the Y-axis direction areset coincident with the angular velocity ω₁ corresponding to the naturalfrequency in the longitudinal direction of the ultrasonic horn 11 forthe X-axis direction and the angular velocity ω₂ corresponding to thenatural frequency of the longitudinal vibrations in the Y-axisdirection, respectively. Consequently, the amplitude at the intersectingcoupling position of the pair of ultrasonic horns 11 and 12 becomes amaximum amplitude. In other words, the angular velocities ω₁ and ω₂ ofthe vibrations in the two directions are selected based on the design ofthe ultrasonic horns 11 and 12.

First, excitation with vibrations of x=Acosω₁t by the ultrasonicoscillator 13 for the X-axis direction is described. Referring to FIG.3, the length of the ultrasonic horn 11 for the X-axis direction isdesigned equal to the length of one wavelength of longitudinalvibrations of the ultrasonic horn 11 by ultrasonic vibrations. Further,the fixed rods 16 are fixed at the positions of 0.5 wavelengths. It isto be noted that the fixed rods 16 may be formed integrally with or asseparate members from the ultrasonic horn 11.

In FIG. 3, the amplitude of the longitudinal vibrations in the X-axisdirection is represented by a displacement in the Y-axis direction forthe convenience of illustration. The amplitude of the longitudinalvibrations of the ultrasonic horn 11 exhibits its maximum amplitude atthe movable pressurization point of the ultrasonic horn 11 at which thepresser 22 is provided. Also, the ultrasonic horn 12 for the Y-axisdirection is fixed by the fixed rods 18 similarly.

The third order natural frequency of vibrations in the X-axis directionof the ultrasonic horn 12 for the Y-axis direction, that is, transversevibrations, is set so as to coincide with the natural frequency ofultrasonic vibrations in the X-axis direction. Accordingly, when themovable pressurization point tends to move in the X-axis direction by alongitudinal vibration of the ultrasonic horn 11 for the X-axisdirection, a third order transverse vibration of the ultrasonic horn 12for the Y-axis direction is excited, and the ultrasonic horn 12 for theY-axis direction forms such an amplitude vibration as shown in FIG. 3.Accordingly, the intersecting position between the ultrasonic horn 11for the X-axis direction and the ultrasonic horn 12 for the Y-axisdirection, that is, the movable pressurization point, moves with asubstantially same vibration x=Acosω₁t in the X-axis direction as shownin FIG. 3.

Then, in such a state as described above, vibrations of y=Bcos(ω₂2t−α)are applied to the ultrasonic horn 12 for the Y-axis direction by meansof the ultrasonic oscillator 14. Here, since the angular velocity of thethird order natural frequency in the transverse direction between thefixed rods 16 of the ultrasonic horn 11 for the X-axis direction is setso as to coincide with ω₂, the movable pressurization point moves withthe substantially same vibration y=Bcos(ω₂t−α) in the Y-axis directionsimilarly, as described above.

Consequently, the intersecting position of the ultrasonic horns 11 and12 at which the presser 22 is provided, that is, the movablepressurization point, is transversely vibrated in both of the X-axisdirection and the Y-axis direction. The vibration states of thecross-shaped ultrasonic horns in this state are shown in FIG. 4. Inparticular, FIG. 4 shows only patterns of the transverse vibrations ofthe ultrasonic horns 11 and 12. Accordingly, if the amplitudes A and Bof the vibrations then and the angular velocities ω₁ and ω₂ of and thephase difference α between the vibrations are selected in such a manneras given in the following table, the locus by the vibrations of themovable pressurization point at which the presser 22 is provided becomessuch as given below. The locus of the end of the vector of the compositevibrations then is represented by the patterns of FIGS. 5(A) to 5(I).

ω A B α x y FIG. When ω₁ = ω₂ = ω A 0 0 Acosωt 0 A 0 B 0 0 Bcosωt B A A0 Acosωt Acosωt C A A 90° Acosωt Asinωt D A A 180° Acosωt −Acos- E ωt AA 270° Acosωt −Asin- F ωt A 2A 90° Acosωt 2Asinωt G When ω₁ = ω, ω₂ = 2ωA A 90° Acosωt Asin2ωt H When ω₁ = ω, ω₂ = ω + Δω A A 90° Acosωt Asin I(ω + Δω)t

Now, use of such an ultrasonic vibration method as described above andthe ultrasonic vibration apparatus which uses the method to bond asemiconductor bare chip 40 and a board 45 to each other is describedwith reference to FIGS. 2 and 6 to 8. The semiconductor chip 40 formedfrom a bare chip has pad electrodes 41 formed along peripheral edgeportions on an electrode face thereof, as shown in FIGS. 6 and 7. It isto be noted that the face on which the pad electrodes 41 are formed iscoated with a surface protecting layer formed from, for example, asilicon nitride layer or a polyimide layer, and only portions thereoffor the pad electrodes 41 are open. Bumps 42 made of a conductor, suchas a metal, are formed on such pad electrodes 41. Consequently, thesemiconductor chip 40 is formed of the peripheral pad type.

On the other hand, the board 45 onto which the semiconductor chip 40 isto be flip chip mounted is made of, for example, a ceramics typematerial, and electrodes formed from lands 46 made of a conductivematerial such as, for example, copper and coated with nickel, gold orthe like by surface plating processing are formed at positions of theboard 45 corresponding to the pad electrodes 41 of the semiconductorbare chip 40 to be mounted. The lands 46 are connected to wiring lineportions formed on the front surface or the rear surface of the board45.

In order to bond the semiconductor chip 40 to the board 45 having such aconfiguration as described above, the board 45 is placed onto a base 47,as shown in FIGS. 2 and 6, and the semiconductor chip 40 is disposed onthe lower side of the presser 22 of the ultrasonic bonding apparatussuch that the surface thereof on which the pad electrodes 41 areprovided is directed downwardly. Then, in this state, the ultrasonicvibrators 13 and 14 are driven by the ultrasonic oscillators 27 and 28to cause the ultrasonic horns 11 and 12 to individually vibratelongitudinally, respectively, such that composite vibrations aregenerated at the position at which the presser 22 is provided. By suchcomposite vibrations, frictional heat is generated between end portionsof the bumps 42 on the pad electrodes 41 and the lands 46 of the board45. Consequently, at least the end portions of the bumps 42 or the lands46 are melted and the pad electrodes 41 and the lands 46 are connectedto each other, whereby such a semiconductor device as shown in FIG. 8 isobtained.

The cross-shaped horns 11 and 12 are moved downwardly in a state whereinthe movable pressurization point formed at the intersecting position ofthe pair of ultrasonic horns 11 and 12 vibrates in various loci, asshown in Table 1 and in FIG. 5, by ultrasonic vibrations in this manner,whereupon the presser 22 presses the semiconductor bare chip 40 againstthe board 45. Since the contact face of the presser 22 with thesemiconductor chip 40 is designed so as to have high friction, thesemiconductor chip 40 is ultrasonically bonded to the electronic circuitboard 45 while drawing the same locus as that of the presser 22. Sincean arbitrary locus can be selected from among such various loci ofvibrations as shown by the patterns of FIGS. 5(A) to 5(I), if a uniformvibration pattern which does not rely upon the arrangement direction ofthe bumps 42 is formed on the electrode face of the semiconductor barechip 40, then a stable bonding quality is obtained.

It is to be noted that, in such an ultrasonic vibration method and anultrasonic variation apparatus as described above, the form or length ofvibrations or the fixed position of each of the ultrasonic horn 11 forthe X-axis direction and the ultrasonic horn 12 for the Y-axis directioncan be selected arbitrarily. For example, it is possible to set thelength of the ultrasonic horn 11 for the X-axis direction equal to thelength of one wavelength of longitudinal vibrations generated with theultrasonic horn 11 and make the first order natural frequency oftransverse vibrations generated with the ultrasonic horn 12 for theY-axis direction coincide with the frequency of ultrasonic vibrations.Consequently, vibrations in the transverse direction of the ultrasonichorn 12 for the Y-axis direction become such as illustrated in FIG. 9.

Alternatively, it is possible to set, as shown in FIG. 10, the length ofthe ultrasonic horn 11 for the X-axis direction to the length of 2wavelengths of longitudinal vibrations generated with the ultrasonichorn 11 and make the third order natural frequency of transversevibrations of the ultrasonic horn 12 for the Y-axis direction coincidewith the frequency of the ultrasonic vibrations.

It is to be noted that, although the shapes and the fixed positions ofthe ultrasonic horn 11 for the X-axis direction and the ultrasonic horn12 for the Y-axis direction shown in FIGS. 9 and 10 are drawnsymmetrically with each other, it is only necessary to design so thatlongitudinal vibrations of the ultrasonic horn 11 for the X-axisdirection and the ultrasonic horn 12 for the Y-axis direction mayresonate with transverse vibrations of the ultrasonic horn 12 for theY-axis direction and the ultrasonic horn 11 for the X-axis direction,respectively, and the ultrasonic horns 11 and 12 may not necessarily beformed symmetrically.

According to a principal aspect of the present invention relating to anultrasonic vibration method, a pair of ultrasonic horns are coupled inan intersecting relationship to each other, and a first one of theultrasonic horns is excited to longitudinally vibrate in a lengthwisedirection thereof so that transverse vibrations are generated with asecond one of the ultrasonic horn while the second ultrasonic horn isexcited to longitudinally vibrate in a longitudinal direction thereof sothat transverse vibrations are generated with the first ultrasonic horn,such that composite vibrations of the transverse vibrations of the pairof ultrasonic horns produced at the intersecting coupling point of thepair of ultrasonic horns are used as an output.

Accordingly, with such an ultrasonic vibration method as just described,vibrations of various loci can be generated at the intersecting couplingposition of the pair of ultrasonic horns in a plane parallel to theplane which includes the pair of ultrasonic horns.

According to a principal aspect of the present invention relating to anultrasonic vibration apparatus, it comprises a pair of ultrasonic hornscoupled in a substantially intersecting relationship to each other in apredetermined plane, an ultrasonic vibrator attached to an end portionof each of the ultrasonic horns, an ultrasonic oscillator for supplyingultrasonic signals to the pair of ultrasonic vibrators, and a presserprovided at the intersecting coupling position of the pair of ultrasonichorns for being pressed against a contact object member; and, the pairof ultrasonic horns are excited to individually vibrate longitudinallysuch that the contact object member is bonded through the presser bycomposite vibrations of transverse vibrations produced at theintersecting coupling position.

Accordingly, with such an ultrasonic vibration apparatus as justdescribed, by pressing the presser provided at the intersecting couplingposition of the pair of ultrasonic horns against the contact objectmember, composite vibrations produced at the intersecting couplingposition of the pair of ultrasonic horns can be applied to the contactobject member, whereby the contact object member can be bonded toanother member while the contact object member is ultrasonicallyvibrated. Thus, an ultrasonic bonding apparatus, which uses ultrasonicvibrations composed of the composite vibrations described above, isprovided.

What is claimed is:
 1. An ultrasonic vibration method, characterized inthat a pair of ultrasonic horns are coupled in an intersectingrelationship to each other and a first one of said ultrasonic horns isexcited to longitudinally vibrate in a lengthwise direction thereof tocause a second one of said ultrasonic horns to generate transversevibrations while the second ultrasonic horn is excited to longitudinallyvibrate in a lengthwise direction thereof to cause the first ultrasonichorn to generate transverse vibrations such that composite vibrations ofthe transverse vibrations of said pair of ultrasonic horns which areproduced at the intersecting coupling position of said pair ofultrasonic horns are used as an output.
 2. An ultrasonic vibrationmethod according to claim 1, characterized in that said pair ofultrasonic horns intersect substantially perpendicularly with each otherand produce the composite vibrations within a plane substantially inparallel to a plane which includes said pair of ultrasonic horns.
 3. Anultrasonic vibration method according to claim 1, characterized in thata presser is provided at the intersecting coupling position of said pairof ultrasonic horns and projected substantially perpendicularly to aplane which includes said pair of ultrasonic horns, and said presser ispressed against a contact object member to transmit the compositevibrations to the contact object member.
 4. An ultrasonic vibrationmethod according to claim 3, characterized in that the contact objectmember is bonded to another member by the composite vibrations.
 5. Anultrasonic vibration method according to claim 1, characterized in thata pair of ultrasonic vibrators for individually providing vibrations tosaid pair of ultrasonic horns are provided, and a phase relationshipbetween ultrasonic signals to be applied to said pair of ultrasonicvibrators is adjusted.
 6. An ultrasonic vibration method according toclaim 5, characterized in that adjustment of the phase of one of saidpair of ultrasonic vibrators is performed to adjust the phaserelationship between the signals to said pair of ultrasonic vibrators.7. An ultrasonic vibration method according to claim 5, characterized inthat the amplitudes or the angular velocities of or the phase differencebetween the ultrasonic signals to be applied to said pair of ultrasonicvibrators are adjusted to vary the locus of the composite vibrations ina plane parallel to a plane which includes said pair of ultrasonichorns.
 8. An ultrasonic vibration method according to claim 1,characterized in that said pair of ultrasonic horns have a lengthsubstantially equal to the wavelength of ultrasonic waves whichpropagate in said pair of ultrasonic horns or substantially equal to anintegral number of times the wavelength.
 9. An ultrasonic vibrationmethod according to claim 1, characterized in that each of said pair ofultrasonic horns is fixed at least at a position of a node.
 10. Anultrasonic vibration method according to claim 8, characterized in thatsaid pair of ultrasonic horns intersect with and are coupled to eachother each at a substantially middle portion in the lengthwise directionthereof such that the amplitude of the longitudinal vibrations ismaximum at the intersecting coupling position, and are each fixed byfixing means at a position spaced by a half wavelength or a distance ofthe sum of a half wavelength and an integral number of times onewavelength from the intersecting coupling position.
 11. An ultrasonicvibration apparatus, characterized in that it comprises a pair ofultrasonic horns coupled in an intersecting relationship to each other,and a first one of said ultrasonic horns is excited to longitudinallyvibrate in a lengthwise direction thereof to cause a second one of saidultrasonic horns to generate transverse vibrations while the secondultrasonic horn is excited to longitudinally vibrate in a lengthwisedirection thereof to cause the first ultrasonic horn to generatetransverse vibrations such that composite vibrations of the transversevibrations of said pair of ultrasonic horns which are produced at theintersecting coupling position of said pair of ultrasonic horns are usedas an output.
 12. An ultrasonic vibration apparatus according to claim11, characterized in that said pair of ultrasonic horns intersectsubstantially perpendicularly with each other and produce the compositevibrations within a plane substantially in parallel to a plane whichincludes said pair of ultrasonic horns.
 13. An ultrasonic vibrationapparatus according to claim 11, characterized in that it furthercomprises a presser provided at the intersecting coupling position ofsaid pair of ultrasonic horns and projected substantiallyperpendicularly to a plane which includes said pair of ultrasonic horns,and said presser is pressed against a contact object member to transmitthe composite vibrations to the contact object member.
 14. An ultrasonicvibration apparatus according to claim 13, characterized in that thecontact object member is bonded to another member by the compositevibrations.
 15. An ultrasonic vibration apparatus according to claim 11,characterized in that it further comprises a pair of ultrasonicvibrators for individually providing vibrations to said pair ofultrasonic horns, and a phase relationship between ultrasonic signals tobe applied to said pair of ultrasonic vibrators is adjusted.
 16. Anultrasonic vibration apparatus according to claim 15, characterized inthat adjustment of the phase of at least one of said pair of ultrasonicvibrators is performed.
 17. An ultrasonic vibration apparatus accordingto claim 11, characterized in that the amplitudes or the angularvelocities of, or the phase difference between, the ultrasonic signalsto be applied to said pair of ultrasonic vibrators are adjusted to varythe locus of the composite vibrations in a substantially same plane. 18.An ultrasonic vibration apparatus according to claim 11, characterizedin that said pair of ultrasonic horns have a length substantially equalto the wavelength of ultrasonic waves which propagate in said pair ofultrasonic horns or substantially equal to an integral number of timesthe wavelength.
 19. An ultrasonic vibration apparatus according to claim11, characterized in that each of said pair of ultrasonic horns is fixedat least at a position of a node by fixing means.
 20. An ultrasonicvibration apparatus according to claim 11, characterized in that saidpair of ultrasonic horns intersect with and are coupled to each othereach at a substantially middle portion in the lengthwise directionthereof such that the longitudinal vibrations exhibits a maximumamplitude at the intersecting coupling position, and each are fixed byfixing means at a position spaced substantially by a half wavelength ora distance of the sum of a half wavelength and an integral number oftimes one wavelength from the intersecting coupling position.
 21. Anultrasonic vibration apparatus according to claim 11, characterized inthat an odd-numbered order natural frequency of the transversevibrations of the first ultrasonic horn substantially coincides with thefrequency of an ultrasonic vibrator of the second ultrasonic horn whichintersects with the first ultrasonic horn such that the transversevibrations thereof substantially resonate with the ultrasonic vibrationsof the second ultrasonic horn.
 22. An ultrasonic vibration apparatus,characterized in that it comprises a pair of ultrasonic horns coupled ina substantially intersecting relationship to each other in apredetermined plane, an ultrasonic vibrator attached to an end portionof each of said ultrasonic horns, an ultrasonic oscillator for supplyingultrasonic signals to the pair of ultrasonic vibrators, and a presserprovided at the intersecting coupling position of said pair ofultrasonic horns for being pressed against a contact object member, andthat said pair of ultrasonic horns are excited to individually vibratelongitudinally such that the contact object member is bonded throughsaid presser by composite vibrations of transverse vibrations producedat the intersecting coupling position.
 23. An ultrasonic vibrationapparatus according to claim 22, characterized in that it furthercomprises phase adjustment means for adjusting the phase of theultrasonic signals to be applied to said pair of ultrasonic vibrators.24. An ultrasonic vibration apparatus according to claim 23,characterized in that said phase adjustment means is provided between atleast one of said ultrasonic vibrators and said ultrasonic oscillator.25. An ultrasonic vibration apparatus according to claim 22,characterized in that the amplitudes or the angular velocities of, orthe phase difference between, the ultrasonic signals to be applied tosaid pair of ultrasonic vibrators are adjusted to vary the locus of thecomposite vibrations in the predetermined plane.
 26. An ultrasonicvibration apparatus according to claim 22, characterized in that one ofsaid ultrasonic horns has a length substantially equal to the wavelengthof ultrasonic waves which propagate in said ultrasonic horns orsubstantially equal to an integral number of times the wavelength. 27.An ultrasonic vibration apparatus according to claim 22, characterizedin that each of said pair of ultrasonic horns is fixed at least at aposition of a node by fixing means.
 28. An ultrasonic vibrationapparatus according to claim 22, characterized in that said pair ofultrasonic horns intersect with and are coupled to each other each at asubstantially middle portion in the lengthwise direction thereof suchthat the amplitude of the longitudinal vibrations is maximum at theintersecting coupling position, and are each fixed by fixing means at aposition spaced by a half wavelength or a distance of the sum of a halfwavelength and an integral number of times one wavelength from theintersecting coupling position.
 29. An ultrasonic vibration apparatusaccording to claim 22, characterized in that an odd-numbered ordernatural frequency of the transverse vibrations of a first one of saidultrasonic horns substantially coincides with the frequency of saidultrasonic vibrator of a second one of said ultrasonic horns whichintersects with the first ultrasonic horn such that the transversevibrations thereof substantially resonate with the ultrasonic vibrationsof the second ultrasonic horn.